SUMMARY OF THE PRIOR ART
Hot box detector systems and associated alarm systems are well know in the art. Typical prior art hot box detectors or the like have been capable of detecting the pressure of an alarm condition and to signal the presence thereof by means of an alarm bell or light and to indicate the location of the alarm condition on a graph or counter. The alarm location was available only from the dispatcher's office which was remote from the train. In order to overcome this problem, a system was devised by DePriest, U.S. Pat. No. 3,226,540, wherein the location of a hot box was reported directly to the train crew immediately after detection thereof as well as to the train dispatcher. One disclosed means of reporting a hot box is an uncoded verbal message.
These prior art systems detected hot box alarm conditions by comparing temperatures on journals on opposite sides of each axle.
The prior art systems therefore failed to detect a hot box condition when both journals were in an overheated state. The prior art also registered an alarm condition based upon fixed temperature differential measurements of journals. This procedure failed to take into account ambient conditions wherein the journal box could be in hot, tropical environs or cold, arctic environs. Also, sun radiated heat has an appreciable effect on the apparent heat radiated from a journal box.
Train trucks at present utilize both sleeve bearings and roller bearings on their axles. Roller bearings radiate approximately twice the apparent heat as compared with sleeve or friction bearings when sensed by the optical heat sensing equipment. The prior art makes no provision for determining the type of bearing being used on the truck under test and have effected a compromise solution which leads to erroneous test results.